There is an ongoing need for pressure sensitive adhesive products (e.g., pressure sensitive tapes and sheeting) having a variety of new properties not possessed by current products. One way to achieve new properties or tailor the properties of a pressure sensitive adhesive products through the use of multilayer constructions.
Products having more than one layer of pressure sensitive adhesive have been described. For example, products are known that consist of layer of a higher modulus pressure sensitive adhesive and a layer of a lower modulus pressure sensitive adhesive. The higher modulus layer provides resistance to creep and the lower modulus layer provides tack.
Multilayer films, both with and without pressure sensitive layers, have also been described. For example, nonpressure sensitive adhesive constructions having up to several thousand layers of alternating polymers with different refractive indices have been shown to have mirror-like properties. Also, films that have tear or puncture resistance have been made by using alternating layers of stiff and ductile polymers. Pressure sensitive adhesive tapes are also known that have multilayered films as the backings on which the pressure sensitive adhesive is coated.
Intermediate layers may be used in a multilayered construction to adhere different polymeric materials having insufficient interlayer adhesion. Intermediate layers, or tie layers, generally have an affinity for both of the principle layers and typically consist of materials that will not significantly reduce the overall tensile properties of the multilayer construction. Some useful tie layers include, for example, copolymers containing blocks that have an affinity for each of the principle layers, which flow when melted and cool to a tack-free state. Tie-layer adhesives are typically hot melt adhesives as opposed to pressure sensitive adhesives.
Although a variety of properties have been accomplished with such pressure sensitive adhesive tapes, there is still a need for pressure sensitive adhesive products, particularly multilayered products.